1. Field of the Invention
The present invention relates to a display comprising an optical imager designed to enable information of the image or multimedia type to be projected, and preferably associated with a lens. The term “lens” is used herein to designate an optical system that is suitable in particular for being positioned in an eyeglass frame.
2. Description of Related Art
Patent U.S. Pat. No. 5,886,822 discloses a lens that presents a projection insert. Such a projection insert is constituted by an optical imager suitable for shaping light beams coming from an electronic and optical system for generating light beams on the basis of an electronic signal, of the miniature screen, laser diode, or light-emitting diode (LED) type. The optical imager directs the light beams towards the wearer's eye in order to enable the information content to be viewed.
By way of example, the optical imager of the invention is of the same type as that described in above-mentioned patent U.S. Pat. No. 5,886,822.
With reference to FIG. 1, an electronic signal carrying information is taken to a miniature screen 1 by a cable 7. On the basis of this signal, the miniature screen 1 illuminated by a back light, generates a pixel image corresponding to the information. By way of example, it is possible to use a “Kopin Cyberdisplay 320 color” screen that generates 320×240 pixel images and that presents dimensions of 4.8 millimeters (mm)×3.6 mm. The screen 1 is put into a reference position relative to the optical imager 5 by means of a mechanical interface. A protective housing protects the assembly in full or in part. Optical components 8, here a mirror and a lens, are associated with the screen 1.
The optical imager 5 comprises a propagation prism 5a, a counter-prism 5b, a quarterwave plate 5c, and a spherical Mangin mirror 5d. The spherical Mangin mirror is a plano-spherical lens with its spherical face made reflective by means of aluminum or equivalent treatment.
The imager 5 also includes polarization separation treatment 6 that may be implemented in the form of a deposit of thin layers, either on the propagation prism 5a or on the counter-prism 5b or by means of a film that is stuck between the two above-described elements.
In this example, the imager 5 is molded in the lens 9 and the housing is placed flat against the back of the lens, with reflective treatment 5e then being included in the lens. On the same principle, the housing may be disposed to one side of the lens 9, in which case the reflective element 5e is omitted.
The term “lens” is used to designate in particular an optionally corrective lens that is designed to be mounted in an eyeglass frame. This ophthalmic eyeglass lens presents traditional eyesight correcting, anti-reflection, anti-dirtying, and anti-scratching functions, for example.
The following arrangement is known for fastening the light beam generator system on the lens and also for enabling focusing to be adjusted so as to adjust the viewing distance of the information image, and consequently so as to provide the wearer with a view that is clear and comfortable. The lens is secured to an adapter constituted by a plate carrying two rods having the housing of the light beam generator system slidably engaged thereon. While making the adjustment, the housing is engaged manually to a greater or lesser extent on the slideways so as to adjust its distance, and subsequently it is locked in place by a transverse screw.
That connection and focus-adjusting device presents the following technical problems.
Depending on the depth of the engagement, the overall size of the display varies. This can give rise to constraints in the way it is made.
That type of device inevitably leads to a large amount of slack between the rods and the slideways, which can be prejudicial to the accuracy of the display.
The housing is generally made of plastics material and the plate and its rods are made of metal. As a result the housing wears quickly, thereby further increasing slack and inaccuracy of the display.
Finally, in that prior art, adjustment is performed manually in the sense that the wearer needs to take hold of the housing and slide it on the rods until good focusing is obtained. Naturally, such an arrangement is not very accurate and not very comfortable to use, being ill-suited to everyday use of a non-experimental kind.
Consequently, it is possible to envisage making a display that is fitted with a focus-adjustment device that acts by adjusting the length of the light beams between the optical elements and the imager, in which said adjustment device is included in the light beam generator system, the light beam generator system including, for example, a stationary plate having connected thereto at least one of the optical elements by means of a movable connection that is adjustable by using an actuator device.
Consequently, the connection between the light beam generator system and the lens no longer needs to enable distance to be adjusted, but it'must remain relatively discreet on the lens for reasons of appearance while nevertheless enabling it to be positioned and held in position accurately, and while also being easy to put into place.
For that purpose, patent document FR 2 885 229 proposes an ophthalmic display having an optical imager designed to shape light beams emitted by a miniature screen of a light beam generator system, which beams are introduced into said imager via an inlet face, the imager serving to direct them towards the eye of the wearer in order to enable an image to be viewed, an adapter being in a referenced position relative to the imager, and the light beam generator system including a connection arrangement connecting it to the adapter, the connection between the system and the adapter being releasable.
The adapter is constituted by two snap-fastening hooks designed to be received in housings carried by the connection arrangement. The hooks are anchored in bores arranged in the inlet face of the imager.
The connection arrangement carried by the light beam generator system includes two substantially parallel arms each carrying one of the snap-fastening housings, one of the housings being carried by a tongue arranged in one of the arms, referred to as the top arm, that is elastically deformable in a direction substantially parallel to an axis joining the axes of the housings and that is directed substantially perpendicularly to said axis.
The connection arrangement carried by the light beam generator system also includes two thrust pegs, each peg being carried by a respective arm and one of the pegs being carried by a rod that is formed in the bottom arm, being elastically deformable in a direction substantially perpendicular to an axis joining the axes of the housings and being directed substantially perpendicularly to said axis. The thrust pegs are placed on opposite sides of a longitudinal plane of the connection arrangement containing said axis.
Although the number of parts used is thus minimized, it is nevertheless found that that connection arrangement does not give complete satisfaction, since its positioning and its movements for the purpose of snap-fastening the two arms on the hooks are relatively complex. They also require the deformable tongue to be pushed so as to deform and as a result they require a force to be applied to the hooks, which are consequently rendered fragile.